The present invention relates to a method of mounting flexible circuit boards on a display device, which contains driver circuits mounted thereon, by using the flexible circuit boards, and more specifically relates to such a method suitable for a liquid crystal display device.
A method of mounting flexible circuit boards equipped with driver circuits in a conventional display device has been disclosed in Japanese Patent Publication No. 3054135. FIG. 11 is a Figure to explain a method of mounting flexible circuit boards in the conventional art for liquid crystal display device. In the view, reference numeral 1 shows an insulating substrate, reference numeral 4 shows flexible circuit boards, reference numeral 5 shows driver circuits, and reference numeral 8 shows common signal lines.
In FIG. 11 the common signal lines, which are commonly connected to each driver circuit, are connected with the flexible circuit boards 4 having the driver circuits on the insulating substrate 1 via an ACF (Anisotropic Conductive Film). As a result, the structure for providing the common signal lines may become smaller, compared with the conventional structure where the common signal lines are formed on PCBs (Printed Circuit Boards) provided separately, thereby further making the frame area smaller in the display device.
However, the above-mentioned conventional art has the following problems. A problem is that it is necessary to form patterns on the insulating substrate due to connecting the common signal lines 8 via patterns 8. Another problem is that in connecting the common signal lines between two adjacent flexible circuit boards, two times as many terminals as the number of the common signal lines are formed and connected after the terminals of the flexible circuit board side and the terminals of the insulating substrate side are positioned, which makes it difficult to improve connection reliability. Further another problem is that the flexible circuit boards are mounted at substantially the same intervals on the insulating substrate as in each flexible circuit board, which makes it difficult to achieve high density packaging that has been demanded due to the high precision of the display devices in recent years.